US20190128747A1 - Sensor apparatus - Google Patents
Sensor apparatus Download PDFInfo
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- US20190128747A1 US20190128747A1 US16/231,745 US201816231745A US2019128747A1 US 20190128747 A1 US20190128747 A1 US 20190128747A1 US 201816231745 A US201816231745 A US 201816231745A US 2019128747 A1 US2019128747 A1 US 2019128747A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/18—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer
- G01K7/20—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a linear resistance, e.g. platinum resistance thermometer in a specially-adapted circuit, e.g. bridge circuit
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D3/00—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups
- G01D3/028—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure
- G01D3/036—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure on measuring arrangements themselves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L19/00—Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
- G01L19/04—Means for compensating for effects of changes of temperature, i.e. other than electric compensation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges
- G01L9/045—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges with electric temperature compensating means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/06—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of piezo-resistive devices
- G01L9/065—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of piezo-resistive devices with temperature compensating means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/14—Measuring resistance by measuring current or voltage obtained from a reference source
Definitions
- the present disclosure relates to a sensor apparatus including a sensor that includes a resistor bridge circuit.
- a pressure sensor may include a resistor bridge circuit which uses a diffused resistor and have a temperature characteristic. When a pressure is detected by a pressure sensor, it may be necessary to perform a correction according to the temperature characteristic.
- a constant current source may be connected between diagonal output terminals of a resistor bridge circuit to acquire temperature information of a pressure sensor,
- a temperature detection circuit is configured to form a first path for supplying a current to one of positive-side and negative-side differential output terminals of a sensor that includes a resistor bridge circuit and a second path for draining a current from the other differential output terminal, the first path and the second path being switchable with respect to the two differential output terminals.
- a controller may cause a voltage measurement portion to measure a voltage of each of the two differential output terminals.
- a calculator may calculate a difference between the voltages of the two differential output terminals to acquire temperature information of the sensor.
- FIG. 1 is a diagram illustrating a configuration of a sensor apparatus in a first embodiment
- FIG. 2 is a diagram illustrating a state in which switch circuits SP 1 and SP 2 of a temperature detection circuit are ON;
- FIG. 3 is a diagram illustrating a state in which switch circuits SM 1 and SM 2 of the temperature detection circuit are ON;
- FIG. 4 is a diagram illustrating a control sequence of the sensor apparatus
- FIG. 5 is a diagram illustrating an error relative to an approximate expression according to a resistance ratio ( ⁇ R/Rs);
- FIG. 6 is a graph with a horizontal axis representing a logarithm of the resistance ratio ( ⁇ R/Rs) and a vertical axis representing the error;
- FIG. 7 is a diagram illustrating the configuration of a sensor apparatus in a second embodiment
- FIG. 8 is a diagram illustrating the configuration of a sensor apparatus in a third embodiment
- FIG. 9 is a diagram illustrating a control sequence of a sensor apparatus in a fourth embodiment:
- FIG. 11 is a diagram illustrating the configuration of a sensor apparatus in a fifth embodiment
- FIG. 12 is a diagram illustrating a sample hold circuit
- FIG. 13 is a diagram illustrating a control sequence of the sensor apparatus
- FIG. 14 is a diagram illustrating a state in which switch circuits SP 1 and SP 2 of a temperature detection circuit are ON when there is a break on a differential output terminal Vinp side in a sensor apparatus in a sixth embodiment
- FIG. 15 is a diagram illustrating a state in which switch circuits SM 1 and SM 2 are ON when there is a break on the differential output terminal Vinp side;
- FIG. 16 is a diagram illustrating a state in which the switch circuits SP 1 and SP 2 of the temperature detection circuit are ON when there is a break on a differential output terminal Vinm side;
- FIG. 17 is a diagram illustrating a state in which the switch circuits SM 1 and SM 2 are ON when there is a break on a differential output terminal Vinm side;
- FIG. 18 is a diagram illustrating a comparative example.
- a sensor apparatus 1 of the present embodiment includes a pressure sensor 2 that includes four resistor elements Rs configuring a resistor bridge circuit.
- a pressure sensor 2 that includes four resistor elements Rs configuring a resistor bridge circuit.
- one pair of the opposite corners of the resistor bridge is connected between a power source and ground.
- Each of differential output terminals Vinp and Vinm corresponding to the other pair of the opposite corners of the resistor bridge is connected to an input terminal of a voltage measurement portion 3 .
- the voltage measurement portion 3 measures a voltage of each of the differential output terminals Vinp and Vinm.
- the voltage measurement portion 3 may be referred to as a voltage measurement circuit.
- a temperature detection circuit 4 is connected between the differential output terminals Vinp and Vinm.
- the temperature detection circuit 4 includes a series circuit which is connected between the output terminal Vinp and the power source and includes a resistor element Rd and a switch circuit SP 1 , and a series circuit which is connected between the output terminal Vinp and the ground and includes a resistor element Rd and a switch circuit SM 2 .
- the temperature detection circuit 4 further includes a series circuit which is connected between the output terminal Vinm and the power source and includes a resistor element Rd and a switch circuit SM 1 , and a series circuit which is connected between the output terminal Vinm and the ground and includes a resistor element Rd and a switch circuit SP 2 .
- a controller 5 performs ON/OFF control for the switch circuits SP 1 and SP 2 as well as SM 1 and SM 2 of the temperature detection circuit 4 .
- a calculator 6 performs an operation on the voltage of each of the differential output terminals Vinp and Vinm measured by the voltage measurement portion 3 to acquire information of a pressure detected by the pressure sensor 2 and temperature information for correcting the pressure.
- the series circuit including the switch circuit SP 1 and the resistor element Rd, the series circuit including the switch circuit SP 2 and the resistor element Rd, the series circuit including the switch circuit SM 1 and the resistor element Rd, and the series circuit including the switch circuit SM 2 and the resistor element Rd correspond to a first series circuit, a fourth series circuit, a second series circuit, and a third series circuit, respectively.
- the controller 5 turns off all of the switch circuits SP 1 and SP 2 as well as SM 1 and SM 2 of the temperature detection circuit 4 to produce a state illustrated in FIG. 1 .
- the controller 5 causes the voltage measurement portion 3 to measure a differential voltage for obtaining information of a pressure detected by the pressure sensor 2 .
- This method is similar to a common method.
- the pressure information is obtained by Expression (1) by measuring the voltage of each of the differential output terminals Vinp and Vinm of the pressure sensor 2 .
- the controller 5 turns on the switch circuits SP 1 and SP 2 of the temperature detection circuit 4 and turns off the switch circuits SM 1 and SN/ 12 of the temperature detection circuit 4 to produce a state illustrated in FIG. 2 .
- the controller 5 causes the voltage measurement portion 3 to measure a differential voltage for obtaining temperature information of the pressure sensor 2 .
- a first path for drawing a sink current from the power source is formed on the output terminal Vinp side of the pressure sensor 2
- a second path for supplying a source current to the ground is formed on the output terminal Vinm side.
- a voltage measured in this state is denoted by a temperature P (Vinp ⁇ Vinm) which is expressed by expression (2).
- the controller 5 turns off the switch circuits SP 1 and SP 2 of the temperature detection circuit 4 and turns on the switch circuits SM 1 and SM 2 of the temperature detection circuit 4 to produce a state illustrated in FIG. 3 .
- the controller 5 causes the voltage measurement portion 3 to measure a differential voltage for obtaining temperature information of the pressure sensor 2 .
- the first path and the second path are switched in such a manner that the second path is formed on the output terminal Vinp side and the first path is formed on the output terminal Vinm side.
- a voltage measured in this state is denoted by a temperature M (Vinp ⁇ Vinm), which is expressed by expression (3).
- the calculator 6 calculates a difference therebetween to obtain temperature information of the pressure sensor 2 .
- the temperature information is obtained on the condition that a resistance value of the resistor element Rs of the pressure sensor 2 is sufficiently larger than a resistance value AR which changes according to pressure.
- the resistance value ⁇ R is not included.
- the voltage (the temperature P ⁇ the temperature M) does not include information of the pressure detected by the pressure sensor 2 and reflects the temperature characteristic of the pressure sensor 2 .
- the pressure detected by the pressure sensor 2 can be corrected according to the temperature characteristic by acquiring the temperature information of the pressure sensor 2 in this manner.
- the sensor apparatus 1 sequentially and repeatedly executes the phases (A), (B), and (C).
- the calculator 6 calculates a difference between the temperature P and the temperature M measured in the previous period to obtain the voltage (the temperature P ⁇ the temperature M). An operation for correcting the pressure may be performed as needed.
- the error relative to the approximate expression according to a resistance ratio is as illustrated in FIGS. 5 and 6 .
- the resistance ratio ( ⁇ R/Rs) may be appropriately set within a range in which an error is allowed.
- the temperature detection circuit 4 is configured to form the first path for supplying a current to one of the positive-side and negative-side differential output terminals Vinp and Vinm of the pressure sensor 2 which includes the resistor bridge circuit and the second path for draining a current from the other differential output terminal, the first path and the second path being switchable with respect to the two differential output terminals Vinp and Vinm.
- the controller 5 causes the voltage measurement portion 3 to measure the voltage of each of the two differential output terminals Vinp and Vinm for a case where the first path is formed in one of the differential output terminals and the second path is formed in the other differential output terminal by the temperature detection circuit 4 and for a case where the second path is formed in the one differential output terminal and the first path is formed in the other differential output terminal by the temperature detection circuit 4 .
- the calculator 6 calculates the difference between the voltages of the differential output terminals Vinp and Vinm to acquire temperature information of the pressure sensor 2 .
- Such a configuration makes it possible to eliminate the necessity of a constant current source and acquire temperature information of the pressure sensor 2 with the S/N ratio maintained without lowering the sensor sensitivity as in a related art.
- the temperature detection circuit 4 includes the first series circuit that is connected between the differential output terminal Vinp and the power source and includes the resistor element Rd and the switch circuit SP 1 , the second series circuit which is connected between the differential output terminal Vinm and the power source and includes the resistor element Rd and the switch circuit SM 1 , the third series circuit which is connected between the differential output terminal Vinp and the ground and includes the resistor element Rd and the switch circuit SM 2 , and the fourth series circuit which is connected between the differential output terminal Vinm and the ground and includes the resistor element Rd and the switch circuit SP 2 .
- a temperature detection circuit 12 includes a series circuit 13 of resistor elements R 1 to R 3 .
- the series circuit 13 is connected between a power source and ground.
- a common connection point between switch circuits SP 1 and SM 1 is connected to a common connection point between the resistor elements R 1 and R 2 .
- a common connection point between switch circuits SP 2 and SM 2 is connected to a common connection point between the resistor elements R 2 and R 3 .
- the resistor elements R 1 to R 3 correspond to first to third resistor elements, respectively.
- the series circuit 13 corresponds to a voltage dividing resistor circuit.
- a voltage amplitude in temperature detection can be variably set by adjusting resistance values of the resistor elements R 1 to R 3 .
- Each of the switch circuits SP and SM is often composed of a MOSFET. In this case, a potential difference with respect to the power source or the ground is given to both ends of the switch circuits SP and SM. Accordingly, a threshold of the FET increases by a substrate effect, and an off-leak current can be reduced.
- the “off-leak” described herein refers to, for example, off-leak on the switch circuit SM side which is OFF when the switch circuit SP side is ON as illustrated in FIG. 2 .
- a temperature detection circuit 22 of a sensor apparatus 21 of a third embodiment includes a first constant current source 23 and a second constant current source 24 instead of the resistor elements Rd of the temperature detection circuit 4 of the first embodiment.
- One end of the first constant current source 23 is connected to a power source.
- One end of the second constant current source 24 is connected to ground.
- a common connection point between switch circuits SP 1 and SM 1 is connected to the other end of the first constant current source 23 .
- a common connection point between switch circuits SP 2 and SM 2 is connected to the other end of the second constant current source 24 .
- the constant current sources 23 and 24 of the third embodiment are connected in parallel to the pressure sensor 2 .
- a voltage applied to the pressure sensor 2 is not reduced as in a related art.
- the temperature P and the temperature M which are measured to acquire temperature information in the above embodiments, are added to also acquire information of a pressure detected by a pressure sensor 2 .
- expression (6) also corresponds to a pressure sensitivity of a sensor apparatus 1 .
- the temperature sensitivity is obtained by expression (7).
- a calculator 6 acquires information of a pressure detected by the pressure sensor 2 by adding the temperature P and the temperature M. Thus, it is possible to reduce the time required for a control sequence. Further, it is possible to maximize the temperature sensitivity by setting the resistance value of the resistor element Rd to half a resistance value of a resistor element Rs of the pressure sensor 2 .
- a sensor apparatus 31 of a fifth embodiment includes two pairs of pressure sensors 2 and temperature detection circuits 4 .
- One of the pairs includes a pressure sensor 2 (0) and a temperature detection circuit 4 (0), and the other pair includes a pressure sensor 2 (1) and a temperature detection circuit 4 (1).
- a voltage measurement portion 32 includes a sample hold circuit 33 which is built therein and includes a sample circuit portion 33 S and a hold circuit portion 33 H.
- the sample hold circuit 33 includes sample circuit portions 33 S (0) and 33 S (1) which correspond to pressure sensors 2 (0) and 2 (1), respectively.
- the sample circuit portion 33 S includes switch circuits 41 p and 41 m as well as 42 p and 42 m of the input side, and 43 p and 43 m as well as 44 p and 44 m of the output side.
- a common connection point between the switch circuits 42 p and 42 m and a common connection point between the switch circuits 44 p and 44 m are both connected to ground.
- Capacitors 45 p and 45 m for sampling are connected between the switch circuits 41 p and 43 p and between the switch circuits 41 m and 43 m, respectively,
- the hold circuit portion 33 H includes a differential amplifier 46 .
- a parallel circuit of a capacitor 47 p for holding and a switch circuit 48 p is connected between an inverting input terminal and a noninverting output terminal of the differential amplifier 46 .
- a parallel circuit of a capacitor 47 m and a switch circuit 48 m is connected between a noninverting input terminal and an inverting output terminal of the differential amplifier 46 .
- the switch circuits 43 p and 43 m are connected to the inverting input terminal and the noninverting input terminal of the differential amplifier 46 , respectively.
- a controller 35 illustrated in FIG. 11 also controls ON/OFF of each of the switch circuits of the sample hold circuit 33 .
- a voltage signal held by the sample hold circuit 33 is input to an A/D converter 34 , converted to digital data, and input to a calculator 6 .
- a first phase (A) the voltage measurement portion 32 samples a measurement result of the pressure (0) of the pressure sensor 2 (0).
- the voltage measurement portion 32 samples a measurement result of the pressure (1) of the pressure sensor 2 (1) in parallel with holding the measurement result of the pressure (0) of the pressure sensor 2 (0).
- the voltage measurement portion 32 holds the measurement result of the pressure (1) of the pressure sensor 2 (1) in parallel with sampling a measurement result of the pressure (0) of the pressure sensor 2 (0).
- the controller 35 switches each of the switch circuits of the temperature detection circuits 4 (0) and 4 (1) corresponding to the control sequence.
- the control sequence can be shortened by performing sampling of a measurement result in one of the pairs in parallel with holding of a measurement result in the other pair.
- the occurrence of a break between one of the differential output terminals Vinp and Vinm of the pressure sensor 2 and the voltage measurement portion 3 , for example, in the configuration of the first embodiment is detected.
- a temperature P and a temperature M are measured, and a difference therebetween is calculated in a manner similar to the first embodiment.
- a result of the calculation is as expressed by expressions (8) to (10).
- FIGS. 16 and 17 illustrate a case where there is a break on the differential output terminal Vinm side.
- a temperature P and a temperature M are measured, and a difference therebetween is calculated in a manner similar to the case where there is a break on the differential output terminal Vinp side.
- a result of the calculation is as expressed by expressions (11) to (13).
- a calculator 6 is capable of detecting a break in the differential output terminal of the pressure sensor 2 by recognizing that the difference between the two voltages (the temperature P and the temperature M) exceeds an upper limit value.
- the sensor is not limited to the pressure sensor, and may be any sensor that includes a resistor bridge circuit.
- three or more pairs of pressure sensors 2 and temperature detection circuits 4 may be provided.
- the embodiments may be implemented in an appropriately combined manner.
- the constant current source is connected in series between a power source and the resistor bridge circuit in actuality, as illustrated in FIG. 18 .
- the actual circuit needs to be operated between the power source and ground.
- the configuration should be as illustrated in FIG. 18 inevitably. Accordingly, a voltage applied to the resistor bridge circuit is reduced by an amount of a voltage drop in the constant current source. As a result, there arises a difficulty of deterioration of an S/N ratio caused by a reduction in sensor sensitivity.
- a temperature detection circuit is configured to form a first path for supplying a current to one of positive-side and negative-side differential output terminals of a sensor that includes a resistor bridge circuit and a second path for draining a current from the other differential output terminal, the first path and the second path being switchable with respect to the two differential output terminals.
- a controller causes a voltage measurement portion to measure a voltage of each of the two differential output terminals for a case where the first path is formed in one of the differential output terminals and the second path is formed in the other differential output terminal by the temperature detection circuit and for a case where the second path is formed in the one differential output terminal and the first path is formed in the other differential output terminal by the temperature detection circuit.
- a calculator calculates a difference between the voltages of the two differential output terminals to acquire temperature information of the sensor.
- the temperature detection circuit includes: a first series circuit connected between the positive-side differential output terminal and the power source and including a resistor element and a switch circuit; a second series circuit connected between the negative-side differential output terminal and the power source and including a resistor element and a switch circuit; a third series circuit connected between the positive-side differential output terminal and the ground and including a resistor element and a switch circuit; and a fourth series circuit connected between the negative-side differential output terminal and the ground and including a resistor element and a switch circuit.
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Abstract
Description
- The present application is a continuation application of International Patent Application No. PCT/JP2017/019219 filed on May 23, 2017, which designated the U.S. and claims the benefit of priority from Japanese Patent Application No, 2016-154534 filed on Aug. 5, 2016. The entire disclosures of all of the above application are incorporated herein by reference.
- The present disclosure relates to a sensor apparatus including a sensor that includes a resistor bridge circuit.
- A pressure sensor may include a resistor bridge circuit which uses a diffused resistor and have a temperature characteristic. When a pressure is detected by a pressure sensor, it may be necessary to perform a correction according to the temperature characteristic. For example, a constant current source may be connected between diagonal output terminals of a resistor bridge circuit to acquire temperature information of a pressure sensor,
- According to one aspect of the present disclosure, a temperature detection circuit is configured to form a first path for supplying a current to one of positive-side and negative-side differential output terminals of a sensor that includes a resistor bridge circuit and a second path for draining a current from the other differential output terminal, the first path and the second path being switchable with respect to the two differential output terminals. A controller may cause a voltage measurement portion to measure a voltage of each of the two differential output terminals. A calculator may calculate a difference between the voltages of the two differential output terminals to acquire temperature information of the sensor.
- The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. In the drawings:
-
FIG. 1 is a diagram illustrating a configuration of a sensor apparatus in a first embodiment; -
FIG. 2 is a diagram illustrating a state in which switch circuits SP1 and SP2 of a temperature detection circuit are ON; -
FIG. 3 is a diagram illustrating a state in which switch circuits SM1 and SM2 of the temperature detection circuit are ON; -
FIG. 4 is a diagram illustrating a control sequence of the sensor apparatus; -
FIG. 5 is a diagram illustrating an error relative to an approximate expression according to a resistance ratio (ΔR/Rs); -
FIG. 6 is a graph with a horizontal axis representing a logarithm of the resistance ratio (ΔR/Rs) and a vertical axis representing the error; -
FIG. 7 is a diagram illustrating the configuration of a sensor apparatus in a second embodiment; -
FIG. 8 is a diagram illustrating the configuration of a sensor apparatus in a third embodiment; -
FIG. 9 is a diagram illustrating a control sequence of a sensor apparatus in a fourth embodiment: -
FIG. 10 is a graph illustrating results obtained by calculatingExpression 6 andExpression 7 where Rs=10 kΩ by changing a resistance value of a resistor element Rd of a temperature detection circuit; -
FIG. 11 is a diagram illustrating the configuration of a sensor apparatus in a fifth embodiment; -
FIG. 12 is a diagram illustrating a sample hold circuit; -
FIG. 13 is a diagram illustrating a control sequence of the sensor apparatus; -
FIG. 14 is a diagram illustrating a state in which switch circuits SP1 and SP2 of a temperature detection circuit are ON when there is a break on a differential output terminal Vinp side in a sensor apparatus in a sixth embodiment; -
FIG. 15 is a diagram illustrating a state in which switch circuits SM1 andSM 2 are ON when there is a break on the differential output terminal Vinp side; -
FIG. 16 is a diagram illustrating a state in which the switch circuits SP1 and SP2 of the temperature detection circuit are ON when there is a break on a differential output terminal Vinm side; -
FIG. 17 is a diagram illustrating a state in which the switch circuits SM1 and SM2 are ON when there is a break on a differential output terminal Vinm side; and -
FIG. 18 is a diagram illustrating a comparative example. - As illustrated in
FIG. 1 , asensor apparatus 1 of the present embodiment includes apressure sensor 2 that includes four resistor elements Rs configuring a resistor bridge circuit. In thepressure sensor 2, one pair of the opposite corners of the resistor bridge is connected between a power source and ground. Each of differential output terminals Vinp and Vinm corresponding to the other pair of the opposite corners of the resistor bridge is connected to an input terminal of avoltage measurement portion 3. Thevoltage measurement portion 3 measures a voltage of each of the differential output terminals Vinp and Vinm. Thevoltage measurement portion 3 may be referred to as a voltage measurement circuit. - A
temperature detection circuit 4 is connected between the differential output terminals Vinp and Vinm. Thetemperature detection circuit 4 includes a series circuit which is connected between the output terminal Vinp and the power source and includes a resistor element Rd and a switch circuit SP1, and a series circuit which is connected between the output terminal Vinp and the ground and includes a resistor element Rd and a switch circuit SM2. Thetemperature detection circuit 4 further includes a series circuit which is connected between the output terminal Vinm and the power source and includes a resistor element Rd and a switch circuit SM1, and a series circuit which is connected between the output terminal Vinm and the ground and includes a resistor element Rd and a switch circuit SP2. - A
controller 5 performs ON/OFF control for the switch circuits SP1 and SP2 as well as SM1 and SM2 of thetemperature detection circuit 4. Acalculator 6 performs an operation on the voltage of each of the differential output terminals Vinp and Vinm measured by thevoltage measurement portion 3 to acquire information of a pressure detected by thepressure sensor 2 and temperature information for correcting the pressure. The series circuit including the switch circuit SP1 and the resistor element Rd, the series circuit including the switch circuit SP2 and the resistor element Rd, the series circuit including the switch circuit SM1 and the resistor element Rd, and the series circuit including the switch circuit SM2 and the resistor element Rd correspond to a first series circuit, a fourth series circuit, a second series circuit, and a third series circuit, respectively. - Next, an action of the present embodiment will be described. As illustrated in
FIG. 4 , in a phase (A), thecontroller 5 turns off all of the switch circuits SP1 and SP2 as well as SM1 and SM2 of thetemperature detection circuit 4 to produce a state illustrated inFIG. 1 . In this state, thecontroller 5 causes thevoltage measurement portion 3 to measure a differential voltage for obtaining information of a pressure detected by thepressure sensor 2. This method is similar to a common method. The pressure information is obtained by Expression (1) by measuring the voltage of each of the differential output terminals Vinp and Vinm of thepressure sensor 2. -
- Then, in a phase (B), the
controller 5 turns on the switch circuits SP1 and SP2 of thetemperature detection circuit 4 and turns off the switch circuits SM1 and SN/12 of thetemperature detection circuit 4 to produce a state illustrated inFIG. 2 . Then, thecontroller 5 causes thevoltage measurement portion 3 to measure a differential voltage for obtaining temperature information of thepressure sensor 2. At this time, a first path for drawing a sink current from the power source is formed on the output terminal Vinp side of thepressure sensor 2, and a second path for supplying a source current to the ground is formed on the output terminal Vinm side. A voltage measured in this state is denoted by a temperature P (Vinp−Vinm) which is expressed by expression (2). -
- Then, in a phase (C), the
controller 5 turns off the switch circuits SP1 and SP2 of thetemperature detection circuit 4 and turns on the switch circuits SM1 and SM2 of thetemperature detection circuit 4 to produce a state illustrated inFIG. 3 . Then, similarly, thecontroller 5 causes thevoltage measurement portion 3 to measure a differential voltage for obtaining temperature information of thepressure sensor 2. In this case, the first path and the second path are switched in such a manner that the second path is formed on the output terminal Vinp side and the first path is formed on the output terminal Vinm side. A voltage measured in this state is denoted by a temperature M (Vinp−Vinm), which is expressed by expression (3). -
- When the two voltages (the temperature P and the temperature M) are measured in this manner, the
calculator 6 calculates a difference therebetween to obtain temperature information of thepressure sensor 2. However, the temperature information is obtained on the condition that a resistance value of the resistor element Rs of thepressure sensor 2 is sufficiently larger than a resistance value AR which changes according to pressure. -
- In expression (4), the resistance value ΔR is not included. Thus, the voltage (the temperature P−the temperature M) does not include information of the pressure detected by the
pressure sensor 2 and reflects the temperature characteristic of thepressure sensor 2. The pressure detected by thepressure sensor 2 can be corrected according to the temperature characteristic by acquiring the temperature information of thepressure sensor 2 in this manner. - As illustrated in
FIG. 4 , thesensor apparatus 1 sequentially and repeatedly executes the phases (A), (B), and (C). In the next period, thecalculator 6 calculates a difference between the temperature P and the temperature M measured in the previous period to obtain the voltage (the temperature P−the temperature M). An operation for correcting the pressure may be performed as needed. - An error [%] between an operation result in expression (4) and an approximate expression to which a condition (Rs>>ΔR) is applied is expressed by expression (5).
-
- For example, when Rs =10 kΩ and Rd=20 kΩ, the error relative to the approximate expression according to a resistance ratio (ΔR/Rs) is as illustrated in
FIGS. 5 and 6 . Thus, the resistance ratio (ΔR/Rs) may be appropriately set within a range in which an error is allowed. - As described above, according to the present embodiment, the
temperature detection circuit 4 is configured to form the first path for supplying a current to one of the positive-side and negative-side differential output terminals Vinp and Vinm of thepressure sensor 2 which includes the resistor bridge circuit and the second path for draining a current from the other differential output terminal, the first path and the second path being switchable with respect to the two differential output terminals Vinp and Vinm. - The
controller 5 causes thevoltage measurement portion 3 to measure the voltage of each of the two differential output terminals Vinp and Vinm for a case where the first path is formed in one of the differential output terminals and the second path is formed in the other differential output terminal by thetemperature detection circuit 4 and for a case where the second path is formed in the one differential output terminal and the first path is formed in the other differential output terminal by thetemperature detection circuit 4. Thecalculator 6 calculates the difference between the voltages of the differential output terminals Vinp and Vinm to acquire temperature information of thepressure sensor 2. Such a configuration makes it possible to eliminate the necessity of a constant current source and acquire temperature information of thepressure sensor 2 with the S/N ratio maintained without lowering the sensor sensitivity as in a related art. - Specifically, the
temperature detection circuit 4 includes the first series circuit that is connected between the differential output terminal Vinp and the power source and includes the resistor element Rd and the switch circuit SP1, the second series circuit which is connected between the differential output terminal Vinm and the power source and includes the resistor element Rd and the switch circuit SM1, the third series circuit which is connected between the differential output terminal Vinp and the ground and includes the resistor element Rd and the switch circuit SM2, and the fourth series circuit which is connected between the differential output terminal Vinm and the ground and includes the resistor element Rd and the switch circuit SP2. With such a configuration, it is possible to form the first path in the positive-side differential output terminal Vinp and form the second path in the negative-side differential output terminal Vinm by simultaneously turning on only the switch circuits SP1 and SP2. Further, it is possible to form the first path and the second path with the positive and negative sides switched by simultaneously turning on only the switch circuits SM1 and SM2. - Hereinbelow, the same part as the first embodiment is designated by the same reference sign, and description thereof will be omitted. Thus, a different part from the first embodiment will be described. As illustrated in
FIG. 7 , in asensor apparatus 11 of the second embodiment, atemperature detection circuit 12 includes aseries circuit 13 of resistor elements R1 to R3. Theseries circuit 13 is connected between a power source and ground. A common connection point between switch circuits SP1 and SM1 is connected to a common connection point between the resistor elements R1 and R2. A common connection point between switch circuits SP2 and SM2 is connected to a common connection point between the resistor elements R2 and R3. The resistor elements R1 to R3 correspond to first to third resistor elements, respectively. Theseries circuit 13 corresponds to a voltage dividing resistor circuit. - In the above configuration, a voltage amplitude in temperature detection can be variably set by adjusting resistance values of the resistor elements R1 to R3. Each of the switch circuits SP and SM is often composed of a MOSFET. In this case, a potential difference with respect to the power source or the ground is given to both ends of the switch circuits SP and SM. Accordingly, a threshold of the FET increases by a substrate effect, and an off-leak current can be reduced. The “off-leak” described herein refers to, for example, off-leak on the switch circuit SM side which is OFF when the switch circuit SP side is ON as illustrated in
FIG. 2 . - As illustrated in
FIG. 8 , atemperature detection circuit 22 of asensor apparatus 21 of a third embodiment includes a first constantcurrent source 23 and a second constantcurrent source 24 instead of the resistor elements Rd of thetemperature detection circuit 4 of the first embodiment. One end of the first constantcurrent source 23 is connected to a power source. One end of the second constantcurrent source 24 is connected to ground. A common connection point between switch circuits SP1 and SM1 is connected to the other end of the first constantcurrent source 23. A common connection point between switch circuits SP2 and SM2 is connected to the other end of the second constantcurrent source 24. - According to the third embodiment configured in the above manner, an effect similar to the effect of the first embodiment can be obtained. The constant
current sources pressure sensor 2. Thus, a voltage applied to thepressure sensor 2 is not reduced as in a related art. - As illustrated in
FIG. 9 , in the fourth embodiment, the temperature P and the temperature M, which are measured to acquire temperature information in the above embodiments, are added to also acquire information of a pressure detected by apressure sensor 2. When a condition (Rd=Rs/2) is set, and (the temperature P+the temperature M) is calculated, a result similar to the result of expression (1) is obtained. -
- Further, expression (6) also corresponds to a pressure sensitivity of a
sensor apparatus 1. The temperature sensitivity is obtained by expression (7). -
- When the expression (6) and the expression (7) where Rs=10 kΩ are calculated by changing a resistance value of a resistor element Rd of a
temperature detection circuit 4, results shown inFIG. 10 are obtained. The results show that the temperature sensitivity is maximum when the condition (Rd=Rs/2) is satisfied. - As described, according to the fourth embodiment, a
calculator 6 acquires information of a pressure detected by thepressure sensor 2 by adding the temperature P and the temperature M. Thus, it is possible to reduce the time required for a control sequence. Further, it is possible to maximize the temperature sensitivity by setting the resistance value of the resistor element Rd to half a resistance value of a resistor element Rs of thepressure sensor 2. - As illustrated in
FIG. 11 , asensor apparatus 31 of a fifth embodiment includes two pairs ofpressure sensors 2 andtemperature detection circuits 4. One of the pairs includes a pressure sensor 2 (0) and a temperature detection circuit 4 (0), and the other pair includes a pressure sensor 2 (1) and a temperature detection circuit 4 (1). Avoltage measurement portion 32 includes asample hold circuit 33 which is built therein and includes asample circuit portion 33S and ahold circuit portion 33H. - As illustrated in
FIG. 12 , thesample hold circuit 33 includessample circuit portions 33S (0) and 33S (1) which correspond to pressure sensors 2 (0) and 2 (1), respectively. Thesample circuit portion 33S includesswitch circuits switch circuits switch circuits Capacitors switch circuits switch circuits - The
hold circuit portion 33H includes adifferential amplifier 46. A parallel circuit of a capacitor 47 p for holding and aswitch circuit 48 p is connected between an inverting input terminal and a noninverting output terminal of thedifferential amplifier 46. A parallel circuit of acapacitor 47 m and aswitch circuit 48 m is connected between a noninverting input terminal and an inverting output terminal of thedifferential amplifier 46. Theswitch circuits differential amplifier 46, respectively. - A
controller 35 illustrated inFIG. 11 also controls ON/OFF of each of the switch circuits of thesample hold circuit 33. A voltage signal held by thesample hold circuit 33 is input to an A/D converter 34, converted to digital data, and input to acalculator 6. - Next, an action of the fifth embodiment will be described. As an operation of the
sample hold circuit 33 is a common operation, detailed description thereof will be omitted. As illustrated inFIG. 13 , in a control sequence of the fifth embodiment, measurement of a pressure (0) of the pressure sensor 2 (0), measurement of a pressure (1) of the pressure sensor 2 (1), measurement of a temperature P (0), measurement of a temperature P (1), measurement of a temperature M (0), and measurement of a temperature M (1) are repeatedly executed. - In a first phase (A), the
voltage measurement portion 32 samples a measurement result of the pressure (0) of the pressure sensor 2 (0). In the next phase (B), thevoltage measurement portion 32 samples a measurement result of the pressure (1) of the pressure sensor 2 (1) in parallel with holding the measurement result of the pressure (0) of the pressure sensor 2 (0). In the next phase (C), thevoltage measurement portion 32 holds the measurement result of the pressure (1) of the pressure sensor 2 (1) in parallel with sampling a measurement result of the pressure (0) of the pressure sensor 2 (0). Thecontroller 35 switches each of the switch circuits of the temperature detection circuits 4 (0) and 4 (1) corresponding to the control sequence. - As described above, according to the fifth embodiment, in the configuration that includes the two pairs of
pressure sensors 2 andtemperature detection circuits 4, and samples and holds each measurement result by thevoltage measurement portion 32, the control sequence can be shortened by performing sampling of a measurement result in one of the pairs in parallel with holding of a measurement result in the other pair. - In a sixth embodiment, the occurrence of a break between one of the differential output terminals Vinp and Vinm of the
pressure sensor 2 and thevoltage measurement portion 3, for example, in the configuration of the first embodiment is detected. As illustrated inFIGS. 14 and 15 , when there is a break on the differential output terminal Vinp side, a temperature P and a temperature M are measured, and a difference therebetween is calculated in a manner similar to the first embodiment. A result of the calculation is as expressed by expressions (8) to (10). -
- A result of expression (10) is 1.5 Vdd under the condition (Rd=Rs/2). That is, an extremely high voltage is detected. Thus, a break can be detected by setting an appropriate threshold and detecting the occurrence of the excessively high voltage.
-
FIGS. 16 and 17 illustrate a case where there is a break on the differential output terminal Vinm side. A temperature P and a temperature M are measured, and a difference therebetween is calculated in a manner similar to the case where there is a break on the differential output terminal Vinp side. A result of the calculation is as expressed by expressions (11) to (13). -
- A result of the expression (13) is also 1.5 Vdd under the condition (Rd=Rs/2). Thus, also in this case, a break can be detected in a similar manner.
- As described above, according to the sixth embodiment, a
calculator 6 is capable of detecting a break in the differential output terminal of thepressure sensor 2 by recognizing that the difference between the two voltages (the temperature P and the temperature M) exceeds an upper limit value. - The sensor is not limited to the pressure sensor, and may be any sensor that includes a resistor bridge circuit.
- In the fifth embodiment, three or more pairs of
pressure sensors 2 andtemperature detection circuits 4 may be provided. - The embodiments may be implemented in an appropriately combined manner.
- Aspects of the disclosure described herein are set forth in the following clauses.
- It is considered that the constant current source is connected in series between a power source and the resistor bridge circuit in actuality, as illustrated in
FIG. 18 . The actual circuit needs to be operated between the power source and ground. Thus, when the direction of current is taken into consideration, the configuration should be as illustrated inFIG. 18 inevitably. Accordingly, a voltage applied to the resistor bridge circuit is reduced by an amount of a voltage drop in the constant current source. As a result, there arises a difficulty of deterioration of an S/N ratio caused by a reduction in sensor sensitivity. - It is an object of the present disclosure to provide a sensor apparatus capable of acquiring temperature information without lowering the sensor sensitivity.
- According to one aspect of the present disclosure, a temperature detection circuit is configured to form a first path for supplying a current to one of positive-side and negative-side differential output terminals of a sensor that includes a resistor bridge circuit and a second path for draining a current from the other differential output terminal, the first path and the second path being switchable with respect to the two differential output terminals. A controller causes a voltage measurement portion to measure a voltage of each of the two differential output terminals for a case where the first path is formed in one of the differential output terminals and the second path is formed in the other differential output terminal by the temperature detection circuit and for a case where the second path is formed in the one differential output terminal and the first path is formed in the other differential output terminal by the temperature detection circuit. A calculator calculates a difference between the voltages of the two differential output terminals to acquire temperature information of the sensor. Such a configuration makes it possible to acquire temperature information of the sensor with the S/N ratio maintained without lowering the sensor sensitivity as in a related art.
- According to one aspect of the present disclosure, the temperature detection circuit includes: a first series circuit connected between the positive-side differential output terminal and the power source and including a resistor element and a switch circuit; a second series circuit connected between the negative-side differential output terminal and the power source and including a resistor element and a switch circuit; a third series circuit connected between the positive-side differential output terminal and the ground and including a resistor element and a switch circuit; and a fourth series circuit connected between the negative-side differential output terminal and the ground and including a resistor element and a switch circuit. With such a configuration, it is possible to form the first path in one of the differential output terminals and form the second path in the other differential output terminal by simultaneously turning on only the switch circuits of the first and fourth series circuits. Further, it is possible to form the first path and the second path with the one differential output terminal and the other differential output terminal switched by simultaneously turning on only the switch circuits of the second and third series circuits.
- While the present disclosure has been described based on the embodiments, it is to be understood that the present disclosure is not limited to the described embodiments and structures. The present disclosure also includes various modifications and modifications within the equivalent range thereof. In addition, various combinations or modes, and other combinations or modes including only one element, more, or less thereof are also included in the scope and idea range of the present disclosure.
Claims (8)
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PCT/JP2017/019219 WO2018025470A1 (en) | 2016-08-05 | 2017-05-23 | Sensor device |
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JP4710119B2 (en) * | 2000-10-27 | 2011-06-29 | Nok株式会社 | Sensor circuit |
DE10133525B4 (en) * | 2001-07-11 | 2010-08-05 | Robert Bosch Gmbh | Sensor with self-test function |
CN1267710C (en) * | 2002-10-23 | 2006-08-02 | 株式会社电装 | Pressure sensing device with temp. sensor |
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JP2006078310A (en) | 2004-09-09 | 2006-03-23 | Nippon Seiki Co Ltd | Semiconductor sensor apparatus |
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US20220291267A1 (en) * | 2021-03-10 | 2022-09-15 | Renesas Electronics America Inc. | Active measurement correction of resistive sensors |
US11747379B2 (en) * | 2021-03-10 | 2023-09-05 | Renesas Electronics America, Inc. | Active measurement correction of resistive sensors |
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